If I understand correctly, the fastners being described are rivets instead of bolts. These hold the bracket or mount on the cross member that in turn supports the transmisson. At least that what are used on my '46 half ton (DP Model).
The parking brake assembly on my '46 is bolted to the side of the transmission with two 1" hex cap bolts 3/8" diameter and 16 threads per inch. The parking brake assembly is held together with rivets.
This assumes (yes dangerous I know) that the previous owner didn't monkey with any of this. I think that is unlikely, but possible.
I'll try to get pictures and a link posted if needed.
